Fluorescence of Metal–Ligand Complexes of Mono- and Di-Substituted Naphthalene Derivatives

In this work, metal ion complexes for several naphthalene derivatives have been investigated. Different working pH values were chosen: 2.5 for complexes with Zr(IV), 4.0 for complexes with Fe(III), 5.0 for complexes with Al(III), and 7.5 for complexes with Cu(II). A stoichiometry of 1:1 for all complexes except two has been established by use of the Benesi–Hildebrand method and the stability constants have been calculated. All complexes between naphthalene derivatives and Cu(II) and Fe(III) show fluorescence quenching. In the case of Al(III), all complexes provided enhanced fluorescence. For Zr(IV), only the complex with 3-hydroxy-2-naphthoic acid provided enhanced fluorescence. The value of the stability constants as a function of the substituents of naphthalene derivatives has been analyzed. One can conclude that Cu(II) showed the largest binding affinity for the mono-substituted derivatives. However, Al(III) and Zr(IV) produced greater selectivity for the di-substituted derivatives. Iron(III) showed no specific binding with any of the naphthalene derivatives.     

Effect of Metal Cation on Absorption and Fluorescence Spectra of Metal Complexes of 8-Hydroxyquinoline∗

8-Hydroxyquinoline complexes of Na(I), Ca(II), Mg(II), Zn(II), Mn(II), Cu(II), Al(III), In(III) and La(III) are synthesized. Photoluminescence and UV-vis absorption spectra of them are reported. Except complexes of Cu(II), and Mn(II), these complexes show photoluminescence. With the increase of polarization force of metal cation, their photoluminescence peaks reveal red-shift and two broad absorption bands in UV-vis absorption spectra appear split and red-shift.

     

“Is Macromolecular Crowding Overlooked?”- Effects of Volume Exclusion on DNA-Amino Acids Complexes and Their Reconstitutes

Biological macromolecules evolve and function within intracellular environments that are crowded with other macromolecules. Crowding results in surprisingly large quantitative effects on both the rates and the equilibria of interactions involving macromolecules, but such interactions are commonly studied outside the cell in uncrowded buffers. The addition of high concentrations of natural and synthetic macromolecules to such buffers enables crowding to be mimicked in vitro, and should be encouraged as a routine variable to study. In this study, we propose to understand the changes in DNA character and its modulation in presence of macromolecules such as PEG with reference to binding parameters to amino acids using fluorescence enhancement.     

Spectral–Luminescence Properties of Molecular Complexes of Photoconductive Polymers with Neutral Organic Acceptors

It has been found that in films of aryl– and alkyl–substituted polysilanes -- poly(methylphenylsilane) and poly(dihexylsilanes) -- the molecules of electron acceptors of tetracyanoquinodimethane, dinitrofluorenone, and trinitrofluorenone form weak complexes with charge transfer from the longest segments of the polymeric chain. The absorption and luminescence spectra of these complexes are similar to the spectra of complexes formed by the carbonyl groups of poly–N–epoxypropyl carbazole with the above acceptors and consist of wide bands situated in the visible range of wavelengths.     

Intermolecular Complexes of Eosin With Resorcinol and β-Napthol

Abstract

The ground state of eosin (2;4;5;7′-tetrabromofluorescein) forms intennolecular complexes with aniline in both aqueous solutions and in 100% EtOH^(1,2). The absorption maxima of these complexes are at 521±1 and 531±1 mu in aqueous solutions and in EtOH respectively whereas the corresponding maxima of uncomplexed eosin are at 516 and 535 mu respectively. Aniline is also a strong quencher of the triplet state⁽³⁾ of eosin and it is associated with a quenchine rate constant of 1.4×10⁹M^?1sec^?1     

Gaseous Metal and the Problem of Vapor–Liquid (Insulator–Metal) Transition in Metal Vapors

Journal of Experimental and Theoretical Physics - We consider the main properties of a gaseous metal, viz., the state of metal vapor adjoining the vapor–fluid transition binodal. The gaseous...     

Optical Absorption Spectrum of Metal–Nitride Complexes of С80 Fullerene as Strongly Correlated Systems

Russian Physics Journal - Within the framework of Hubbard’s model using an approximation of static fluctuations, the energy spectrum of the π-electron subsystem of an icosahedral C80...     

The Effect of Nonlinearity in the Law of Magnetization of a Ferrofluid on the Kelvin–Helmholtz Instability

Technical Physics - The Kelvin–Helmholtz instability arising when a homogeneous gas flow moves over a horizontal surface of a ferrofluid with specified physical properties moving in the same...     

The absorption spectrum of 12C2H2 IV. The regions 7600–9200 cm−1 and 10600–11500 cm−1

The absorption spectrum of ¹²C₂H₂ has been recorded by intracavity laser absorption spectroscopy (ICLAS) in the 10600–11 500 cm^?1 spectral region, where no absorption bands were previously reported. Fifteen bands starting from the vibrational ground state are observed and rotationally analysed. All corresponding excited vibrational levels were assigned using the polyad model, the so-called cluster model (El Idrissi, M.I., Liévin, J., Campargue, A., and Herman, M., 1999, J. chem. Phys., 110, 2074) which allows vibrational energies, rotational B_v constants and, to some respect, relative band intensities to be predicted. Additional data and constants are also provided in the range 7600–9200cm^?1, whenever improving the literature results, from spectra recorded previously at ULB using Fourier transform spectroscopy. The assignment procedure in the range recorded by ICLAS is detailed, leading to a deeper understanding of vibration-rotation and intensity features of the absorption bands within the frame of the cluster model.     

The Dependence of the Luminescence Intensity of Lanthanide Complexes with β-Diketones on the Ligand Form

The influence of -diketone forms on the luminescence intensity of lanthanide compounds in a series of ligands, acetylacetone (trifluoroacetylacetone, benzoylacetone)—their unsaturated analogues (monomeric form)—copolymers of the latter with styrene (methylmethacrylate), was studied. Lanthanides in compounds with copolymers have been established to demonstrate the brightest luminescence. It was found that its intensity depends not only on the character of the substituent (CH₃, CF₃, C₆H₅) in the -diketone molecule, but also on the distance between the -diketone fragments in the copolymer. Reasons explaining the high intensity of luminescence in lanthanide–copolymer compounds are considered.     

Single Molecule Fluorescence of Native and Refolded Peridinin–Chlorophyll–Protein Complexes

Single molecule spectroscopy was applied to study the optical properties of native and refolded peridinin-chlorophyll-protein (PCP) complexes. The native system is a trimer with six chlorophyll a (Chl a) molecules, while the refolded one contains two Chl a and resembles structurally and spectroscopically the PCP monomer. The fluorescence emission of single PCP complexes strongly broadens with increasing excitation power. Simultaneously, the distribution of fluorescence maximum frequencies is also broadened. These spectral changes are attributed to photoinduced conformational changes of the protein that influence the fluorescence of embedded chromophores. Comparison of fluorescence intensities measured for PCP complexes in two different solvents indicates that the native PCP trimers are preserved in EDTA Tris buffer, while in PVA polymer matrix only monomers are stable.     

The Photophysics of β-Tyrosine and Its Simple Derivatives

Synthesis and photophysical studies of (O-methyl)--tyrosine (-tyrosine; an analogue of tyrosine, in which the amino group is moved from the - to the -carbon, closer to the phenol ring) and its derivatives with a blocked amino and/or carboxyl group were performed to explain the nature of the fluorescence of tyrosine derived analogues. All -tyrosine derivatives, except Ac-Tyr(Me), displayed the monoexponential fluorescence decay. The biexponential fluorescence decay observed for Ac-Tyr(Me) is assumed to be the result of the presence of two low-energy conformations (extended and with an intramolecular hydrogen bond). Higher quenching of the fluorescence of -tyrosine derivatives by the N-acetyl group than by the N-methylamide group moved farther was found, contrary to the data found for the respective derivatives of natural tyrosine. The obtained photophysical data are discussed with theoretical calculations (AMBER, AM1) on the basis of the rotamer model.     

The Hubbard model and pressure effects of YBa2Cu3O7−δ superconductors

We apply a mean field approach to the extended Hubbard model on a square lattice to the YBa₂Cu₃O_7−δ family of superconductors under pressure. The parameters of the tight-binding band are taken from experiments, and the coupling strength U and V are estimated by the zero pressure phase diagram (T_c×n_h). This scheme yields the non-trivial dependence of the superconductor critical temperature T_c as a function of the hole concentration n_h in the CuO₂ plane. With the assumption that the pressure P modifies the potential V and the on-plane hole content n_h, we can distinguish the charge transfer and the intrinsic contribution to T_c(P). We show that the changes on T_c(P) for the YBa₂Cu₃O₇ optimally doped compound at low pressures are almost entirely due to the intrinsic term.     

Structural and superconducting properties of Eu1−xPrxBaSrCu3O7−δ

We have investigated the structural and superconducting properties of Eu_1−xPr_xBaSrCu₃O_7−δ by X-ray diffraction analysis, AC and DC magnetization and DC resistivity measurements. The parent compound crystallizes in the orthorhombic symmetry which transforms to tetragonal symmetry at x=0.2. Superconducting transition temperature T_c decreases monotonically with increasing x which approaches zero at x=0.6. The enhancement in critical concentration x_cr observed in Eu_1−xPr_xBa₂Cu₃O_7−δ on replacing 50 at.% Ba by Sr is attributed to the resulting local structural changes.     

Spectral Study of Some Samarium Complexes in the Region 750–250 cm−1

Abstract

Rare earth β -diketonates and diketo-ester complexes are promising laser materials due to narrow line width of the internal 4fⁿ transitions and weak crystal-field interactions¹. The electronic energy states², spectral intensities^3–5, bonding^6,7 and infrared spectra^8–11 of some of these complexes have been recently reported by the authors. However, little information regarding their structure and strengths of various bonds are available. The infrared spectra of rare earth complexes in the spectral region 4000 – 750 cm^?1 are characteristic of the ligand, while those in the region 750 – 250 cm^?1 characterize the metal-ligand bonding. The present communication reports the values of force constants computed from the observed infrared absorption spectra of four ethyl 1-methyl acetoacetate (EMA) and ethylbenzoylacetate (EBA) complexes of trivalent samarium in the region 750 – 250 cm^?1.     

Two Types of Maximally Entangled Bases and Their Mutually Unbiased Property in ℂd⊗ℂd′

We first construct a new maximally entangled basis in bipartite systems \(\mathbb {C}^{d} \otimes \mathbb {C}^{kd}\ (k\in Z^{+})\) which is diffrent from the one in Tao et al. (Quantum Inf. Process. 14, 2291 (2015)), then we generalize such maximally entangled basis into arbitrary bipartite systems \(\mathbb {C}^{d} \otimes \mathbb {C}^{d^{\prime }}\). We also study the mutual unbiased property of the two types of maximally entangled bases in bipartite systems \(\mathbb {C}^{d} \otimes \mathbb {C}^{kd}\). In particular, explicit examples in \(\mathbb {C}^{2} \otimes \mathbb {C}^{4}\), \(\mathbb {C}^{2} \otimes \mathbb {C}^{8}\) and \(\mathbb {C}^{3} \otimes \mathbb {C}^{3}\) are presented.     

The First Observation of 4f-Luminescence in New Heteronuclear Lanthanide–Germanium Complexes

New lanthanide–germanium complexes with diethylenetriaminepentaacetic acid (DTPA) have been synthesized and were characterized by means of elemental analysis, IR-, UV-absorption and luminescent spectroscopy. The 4f-luminescence of heteronuclear Ln(Ge-DTPA)2 (Ln=Sm, Eu, Tb, Dy) complexes in aqueous solutions was investigated for the first time.     

The effect of ultraviolet radiation on water vapour absorption between 5 and 50cm−1

Both field measurements and laboratory experiments suggested that absorption of UV radiation affected the near-millimetre wave absorption by water vapour. Experiments with different flux values and at different temperatures have confirmed this and pumping by UV radiation has been shown to give near-millimetre wave emission.